The purpose of this proposal is to investigate and develop new RNA affinity cleavage reagents for commercial use in humans as anti-viral (including anti-HIV) and anti-cancer agents. The reagents are intended to employ the catalytic endonuclease activity of certain oligonucleotide ribozymes. The research will emphasize chemical modification of oligonucleotides at the 2'-position and/or the phosphate internucleotide linkage to increase the oligonucleotides cell permeability, and increase their resistance to degradation by nucleases. In addition, increasing the catalytic activity will be attempted by optimizing metal ion binding and by increasing the acidity of protons required for general acid catalysis. This will be investigated via modification of the heterocyclic bases. Interesting applications include targeting sites in the c-myc oncogene, as well as 25 potential sites in HIV. A variety of test systems including known in vitro ribozyme assays, an in vitro CAT assay, and cell culture assays employing CAT and c-myc will be used to evaluate the new reagents for use as anti-cancer and anti-viral pharmaceuticals. This approach offers the potential to systematically develop therapeutics by selectively targeting RNA sequences.